In control engineering, a reference governor that modifies a target value of a controlled variable based on future prediction of a state quantity on which a constraint is imposed is known. In PTL 1 an example is described in which a reference governor is used in control of an internal combustion engine. A reference governor is designed to predict how a state quantity on which a constraint is imposed will change from the present to the future with respect to a manipulated variable that is determined based on a target value of a controlled variable, based on the premise that the current operating conditions will also continue thereafter.